Implant

ABSTRACT

An implant, prosthesis and method of use are described. The implant comprises an articulation component having a bearing surface and a reverse surface arranged to couple to a proximal neck portion of an arthroplasty implant coupled to a bone. A collar is arranged to couple to the reverse surface of the articulation component. The collar defines a neck hole arranged to pass around the coupling between the articulation component and the proximal neck portion of the arthroplasty implant. The collar and the articulation component comprise complementary coupling features to secure the collar to the articulation component. The collar further comprises a plurality of attachment portions to couple the collar to bone fragments or soft tissues. The prosthesis comprises the implant and an arthroplasty implant having a distal portion arranged to be coupled to an end of a long bone and a proximal neck portion.

Cross Reference To Related Application

This application is a divisional of U.S. patent application Ser. No.14/008,597, filed Sep. 30, 2013, which is a National Stage 35 U.S.C. 371of International Patent Application PCT/EP2012/052463 filed Feb. 14,2012, which claims priority to United Kingdom Patent Application No.GB1105243.8, filed Mar. 29, 2011 (now abandoned) all of which areincorporated by reference in their entireties.

The present invention relates generally to orthopaedic surgery and inparticular to shoulder prostheses. More particularly, the presentinvention relates to an implant forming part of a humeral prosthesis.Specifically, the implant comprises an articulation component toarticulate against a glenoid implant or a natural glenoid cavity. Thepresent invention also relates to an assembled prosthesis and a shoulderarthroplasty procedure using the humeral prosthesis.

A natural shoulder joint may undergo degenerative changes for a varietyof reasons, for instance arthritis. Alternatively, a shoulder joint maybe fractured or otherwise damaged by an external force. When a shoulderjoint is sufficiently degenerated or damaged it may be necessary toreplace a natural shoulder joint with a prosthetic shoulder joint.Conventional shoulder prostheses comprise a humeral implant, optionallywith a glenoid implant.

Typically, the humeral implant comprises a stem for insertion into abore extending into the intramedullary canal generally along thelongitudinal axis of the bone and an articulation component such as aconvex bearing head. Typically, the articulation component is coupled toa neck portion of the stem which extends from the intramedullary canalat an inclined angle relative to the longitudinal axis of a distalportion of the stem in order to recreate the arrangement of the naturaljoint.

When the upper extremity of the humerus is fractured, the humerusgenerally breaks into several pieces, typically three or four. Inparticular, for a four part fracture as illustrated in FIG. 1, thehumeral head 2 splits off at the level of the anatomical neck indicatedby line 4, the greater tuberosity 6 and lesser tuberosity 8 areseparated from the humeral shaft 10 below the tuberosities and thetuberosities 6, 8 are separated from one another along the bicipetalgroove 12. In a three part fracture the greater or less tuberosity 6, 8remains attached to the humeral head 2. For both three part and fourpart fractures, as there is no longer a blood supply to the humeral head2 necrosis may begin.

For repair of a four part fracture or a three part fracture, the humeralhead is replaced, and the greater and lesser tuberosities are reattachedto the humeral shaft. Known shoulder prostheses for repair of a fourpart fracture provide tabs or fins attached to the stem whichincorporate holes to receive sutures to couple the tuberosities and softtissue such as cuff muscles to the prosthesis. Correct positioning ofthe suture holes is essential to accommodate the differing attachmentpoints of soft tissues to the humerus in a natural joint. Typicallythree and four part humeral fractures are repaired through ahemi-arthroplasty procedure as there may be no damage to the glenoidcavity and so no need for its replacement.

Certain known prostheses suffer from inflexibility in the position ofattachment points for coupling bone fragments and soft tissues to theimplant, which may result in loss of mobility for the repaired joint.

UK patent application 1007656.0 filed on 7 May 2010 in the name of DePuy(Ireland) (and incorporated herein for all purposes) discloses arotatable collar arranged to couple to a neck portion of a humeralimplant, such as a humeral stem which extends into the intramedullarycanal. The collar is arranged to be located between an articulationcomponent and the natural bone surrounding the humeral implant. Thecollar comprises a plate defining a plurality of suture holes orpre-attached sutures around its periphery which allow the detached bonefragments, including the greater and lesser tuberosities to be coupledto the implant. A suture cage may be formed extending from the collararound the detached bone fragments and back to an opposite portion ofthe plate to hold the bone fragments in position. The collar causes thearticulation component to be spaced apart from the bone, and maytherefore interfere with the correct positioning of the articulationcomponent.

It is an object of embodiments of the present invention to obviate ormitigate one or more of the problems of the prior art, whetheridentified herein or elsewhere.

According to a first aspect of the present invention there is providedan implant comprising: an articulation component comprising a bearingsurface and a reverse surface arranged to couple to a proximal neckportion of an arthroplasty implant coupled to a bone; and a collararranged to couple to the reverse surface of the articulation component,the collar defining a neck hole arranged to pass around the couplingbetween the articulation component and the proximal neck portion of thearthroplasty implant, the collar and the articulation componentcomprising complementary coupling features to secure the collar to thearticulation component; wherein the collar further comprises a pluralityof attachment portions to couple the collar to bone fragments or softtissues.

An advantage of the first aspect of the present invention is that thecollar provides a plurality of attachment points for coupling detachedbone fragments and soft tissue to the articulation component. As thearticulation component and the collar are separate the collar can bepositioned in the joint space and bone fragments coupled to the collarwithout the articulation component in place, which therefore providesthe surgeon with more space to operate. The articulation component andthe collar can then be coupled together before securing the articulationcomponent to the arthroplasty implant. The collar passing around thecoupling between the articulation component and the proximal neckportion such that there is no direct contact between the collar and theproximal neck portion.

In preferred embodiments the collar is received in a recess in a reversesurface of the articulation component such that there is no extracomponent between the articulation component and the bone and so no gapbetween the articulation component and the bone due to the collar. Theresult is that the implant appears as a conventional bearing headimplant. When used in combination with an arthroplasty implantsupporting additional attachment points, sutures may be providedextending from the collar to the arthroplasty implant to form a cagesurrounding the bone fragments. This secures the bone fragments inposition and also adds rigidity to the connection between thearticulation component and the distal implant component. The presentinvention is particularly suitable for forming part of a humeralprosthesis to repair three or four part humeral fractures, and inparticular for securing bone fragments including the greater and lessertuberosities.

The reverse surface of the articulation component may comprise a recessand the collar may be arranged to be received in the recess.

The reverse surface of the articulation component may comprise a socketprotruding from the base of the recess and arranged to receive the endof the proximal neck portion of an arthroplasty implant, the recessextending annularly between the socket and a rim defining the boundarybetween the bearing surface and the reverse surface of the articulationcomponent, wherein the neck hole of the collar is arranged to pass overthe socket.

The complementary coupling features may comprise the recess and thecollar having corresponding screw threads. Alternatively, thecomplementary coupling features may comprise one of the recess and thecollar comprising a male part and the other of the recess and the collarcomprising a female part, at least one of the male part and the femalepart being arranged to resiliently deform as the collar is inserted intothe recess such that the male part engages the female part to secure thecollar to the recess. The collar and the recess may respectivelycomprise first and second anti-rotation features that interlock when thecollar is inserted into the recess such that the collar cannot rotatewithin the recess.

The collar may be disc shaped and the attachment portions may beprovided proximal to the periphery of the collar.

At least one of the plurality of attachment portions may comprise asuture hole arranged to receive and secure a first end of a suture.

At least one of the plurality of attachment portions may comprise anattached suture extending from the collar.

According to a second aspect of the present invention there is provideda prosthesis comprising: an implant according to any one of thepreceding claims; and an arthroplasty implant having a distal portionarranged to be coupled to an end of a long bone and a proximal neckportion.

The neck portion may extend along an axis which is inclined to alongitudinal axis of the distal portion, and wherein when the collar iscoupled to the articulation component and the articulation component iscoupled to the proximal neck portion, the collar may lie in a planewhich is perpendicular to the neck axis.

The arthroplasty implant may comprise an arthroplasty plate comprising afixation plate arranged to be secured to a surface of a bone and aconnector assembly extending from the fixation plate to form theproximal neck portion.

The connector assembly may comprise a barrel extending from the fixationplate with a bore which opens through the fixation plate and a connectorrod arranged to slide within the bore of the barrel, and wherein theconnector assembly may incorporate an adjustment mechanism arranged tocause the connector rod to slide into or out of the barrel and a lockingmechanism arranged to lock the position of the connector rod within thebarrel to rigidly space the articulation component apart from thefixation plate.

The fixation plate may comprise a head portion couplable to theconnector assembly and an elongate body portion arranged to extenddistally along the lateral surface of the bone, the elongate bodyportion comprising a plurality of fastener holes arranged to receivebone fasteners for securing the fixation plate to the bone.

The fixation plate head portion may comprise at least one suture holearranged to receive a suture extending from the collar for securing bonefragments and soft tissues to the fixation plate and the collar.

The proximal neck portion may comprise a tapered portion and the reversesurface of the articulation component may comprise a correspondingtapered socket arranged such that when the end of the proximal neckportion is inserted into the tapered socket a taper lock forms securingthe articulation component to the arthroplasty implant.

According to a third aspect of the present invention there is provided asurgical method comprising: removing at least part of an articulatingsurface at an end of a bone; coupling a distal portion of anarthroplasty implant to the end of the bone, the arthroplasty implantfurther comprising a proximal neck portion extending from the distalportion; securing bone fragments to a collar with sutures extendingbetween the bone fragments or attached soft tissue and at least one of aplurality of attachment portions formed in the collar; couplingcomplementary features of the collar and a reverse surface of anarticulation component together to secure the collar to the reversesurface, the articulation component further comprising a bearingsurface; and coupling the articulation component to the proximal neckportion of the arthroplasty plate such that a neck hole of the collarpasses around the coupling between the proximal neck portion of thearthroplasty implant and the articulation component.

Coupling a distal portion of an arthroplasty implant to the end of thebone may comprises: securing a fixation plate forming the distal part ofthe arthroplasty implant to a lateral surface of the fractured end ofthe bone, the fixation plate being coupled to a connector assemblydefining the proximal neck portion and comprising a barrel with a boreand a connector rod, the connector rod being arranged to slide withinthe bore of the barrel; sliding the connector rod into or out of thebarrel to adjust the length of the connector rod extending from thebarrel; and locking the position of the connector rod within the barrelto rigidly space the articulation component apart from the fixationplate.

The fixation plate may further comprise a head portion proximal to thebarrel, the head portion defining at least one suture hole, wherein themethod may further comprise: threading sutures between the attachmentportions of the collar and the at least one suture hole in the headportion of the fixation plate, the sutures passing through bonefragments or attached soft tissue to secure the bone fragments to thecollar and the fixation plate.

The present invention will now be described, by way of example only,with reference to the accompanying drawings, in which:

FIG. 1 illustrates a four part fracture of a proximal humerus;

FIG. 2 illustrates an implant in accordance with a first embodiment ofthe present invention in combination with an arthroplasty plate;

FIG. 3 shows an implant in accordance with a second embodiment of theinvention and the arthroplasty plate of FIG. 2 implanted on an end of ahumerus (the bone being illustrated as transparent to reveal theinternal detail of the implanted arthroplasty plate);

FIG. 4 is an exploded view of the implant of FIG. 2 showing a collarseparated from an articulation component;

FIG. 5 is an assembled view of the implant of FIG. 2;

FIGS. 6a to 6e illustrate steps of a surgical method for implanting theimplant and arthroplasty plate of FIG. 2;

FIG. 7 is an exploded view of an implant in accordance with the secondembodiment of the present invention illustrated in FIG. 3; and

FIG. 8 is a cross sectional view of the assembled implant of FIG. 7.

Referring first to FIG. 2, this illustrates an implant 20 in accordancewith a first embodiment of the present invention and an arthroplastyplate 22. The implant 20 comprises an articulation component 24 arrangedto couple to a proximal neck portion 26 of the arthroplasty plate 22.The implant 20 further comprises a collar 28 arranged to be received ina recess 30 in a reverse surface of the articulation component 24. Itwill be appreciated that in alternative embodiments of the invention thecollar may not be fully received in a recess or there may be no recesssuch that the collar simply couples to a reverse surface of thearticulation component. FIG. 3 illustrates the arthroplasty plate 22coupled to a lateral surface 32 of the proximal humerus 10 such that theproximal neck portion 26 extends through the fractured bone of a threeor four part humeral fracture and couples to implant 20. FIG. 3illustrates an implant 120 in accordance with a second embodiment of thepresent invention coupled to the arthroplasty plate 22. The firstembodiment of the implant 20 is described below in greater detail inconnection with FIGS. 4 and 5. The second embodiment of the implant 120is described below in greater detail in connection with FIGS. 7 and 8.

The arthroplasty plate 22 is described in further detail in UK patentapplication 1101896.7 filed on 4 February 2011 in the name of DePuy(Ireland), which is incorporated herein for all purposes. Thearthroplasty plate 22 will also now be briefly described.

As noted above, conventional humeral implants for a shoulder prosthesiscomprise a stem for insertion into a bore extending into theintramedullary canal of the humerus and an articulation component. Thearticulation component couples to a neck portion of the stem, whichextends from the intramedullary canal at an inclined angle relative tothe longitudinal axis of a distal portion of the stem. However,implanting a humeral stem into the intramedullary canal causessignificant damage to the bone. An arthroplasty plate 22 as illustratedin FIGS. 2 and 3, and as described in greater detail in UK patentapplication 1101896.7 reduces the amount of natural bone that must beremoved as the fixation plate 34 is secured to a lateral surface of thebone. The arthroplasty plate 22 incorporates a length adjustment featurewhich allows the distance between the humeral head implant 20 and thefixation plate 34 to be varied to adjust soft tissue tension in theshoulder joint and to optionally space the humeral head implant 20 awayfrom the bone to avoid further damage to the fractured bone.

The humeral head implant 20 is coupled to the fixation plate 24 via aconnector assembly 38 positioned in a bore formed in the proximalhumerus 32. For repair of a three or four part humeral fracture thehumeral shaft 10 is typically fractured below the greater and lessertuberosities 6, 8. The fixation plate 34 is shaped such that theconnector assembly 38 generally sits above the fracture line and so inpractice it may not be necessary to form a bore, rather portions of thedetached bone fragments may be trimmed to fit around the connectorassembly 38.

The arthroplasty plate 22 is illustrated in a perspective view in FIG.2. The fixation plate 34 comprises an elongate body portion 40 and ahead portion 42 arranged to conform to the surface of the lateralhumerus. The body portion 40 incorporates a number of screw holes 44 forsecuring the plate 40 to the humerus 32 with bone screws 36 as shown inFIG. 3. A slotted screw hole 46 is provided for initial fixation of theplate 40 to the bone. A screw is inserted into the bone through slottedhole 46 allowing the plate 40 to slide along the bone before thefixation plate 40 is permanently attached. Suture holes 48 are providedabout the head portion 42 for securing soft tissues and bone fragmentsto the fixation plate 40. In particular, sutures 50 may extend fromcollar 28 to the head portion 42 of fixation plate 34 to retain bonefragments as illustrated in FIG. 3 and as will be described in greaterdetail below in connection with FIGS. 6a to 6 e.

The plate 34 further comprises an integrally formed hollow barrel 52extending from the plate transverse to the longitudinal axis of theplate, for instance at 135° to recreate the natural anatomy of theproximal humerus. The barrel 52 forms part of the connector assembly 38.The connector assembly 38 further comprises an adjustment mechanism toadjust the distance between a taper 54 and the fixation plate 34. Thetaper 54 is arranged to be received in a corresponding tapered socket inarticulation component 24, as will be described in greater detail below.The connector assembly 38 further comprises a locking mechanism to lockthe adjustment mechanism in position and prevent further movementbetween the taper 54 and the fixation plate 34. In combination theadjustment mechanism and the locking mechanism allow a surgeon toselectively space the articulation component 24 apart from the fixationplate 34 and then lock the components together such that the coupling isrigid. Advantageously the coupling allows the articulation component 24to be spaced apart from the bone such that loads are transferred solelyto the fixation plate, which may be desirable if the humeral head isbadly fractured. The fixation plate 34 extends along the humerussufficiently far to ensure that it can be secured to intact bone.Alternatively, the articulation component 24 may rest upon the bone suchthat load is partially transferred to the natural bone. The adjustmentmechanism allows soft tissue tension within the reduced joint to beadjusted. The connector assembly 38 is not further described herein, butfurther details can be found within UK patent application 1101896.7.

Referring now also to FIGS. 4 and 5, the first embodiment of a humeralhead implant 20 will be described in greater detail. As noted above, thehumeral head implant 20 comprises an articulation component 24 and acollar 28. FIG. 4 shows the articulation component 24 and collar 28separated, and FIG. 5 shows the articulation component 24 and collar 28coupled together.

The articulation component 24 comprises a convex bearing surface 60 anda reverse surface 62 that includes the recess 30. The convex bearingsurface 60 may be defined by a portion of a sphere. The reverse surface62 is substantially taken up by recess 30, which as illustrated extendsacross almost the full width of the reverse surface 62 within rim 64.The recess 30 extends about a socket 66 protrudes from the base of therecess to approximately the level of rim 64. Socket 66 defines a taperedbore and is arranged to form a taper lock to taper 54 at the end of theneck part 26 of arthroplasty plate 22. Specifically, duringimplantation, the articulation component 24 is placed so that taper 54is received in socket 66 and an impaction force is applied to the convexbearing surface 60 to lock the two components together. It will beappreciated that in alternative embodiments of the invention thecoupling between the socket 66 and the proximal neck portion 26 of thearthroplasty implant may vary, for instance they may be coupled by ascrew thread or secured with a grub screw.

Recess 30 forms an annular ring about socket 66. The outer edge ofsocket 66 is provided with screw thread 68. Collar 28 comprises athreaded hole 70 such that rotating articulation component 24 whileholding collar 28 still causes the collar to screw into recess 30 tolock the components together. When assembled, as shown in FIG. 5, thecollar 28 is entirely received within recess 30 such that it is flushwith rim 64, or recessed. Advantageously, this means that the convexbearing head can seat fully upon the bone, if required, unlike thecollar disclosed in UK patent application 1007656.0. Collar 28 furthercomprises holes 72 to receive an instrument to hold the collar 28 stillwhile coupling to the articulation component 24, as is described ingreater detail below in connection with FIGS. 6d and 6 e.

Around the periphery of collar 28 are suture holes 74. A suture can bethreaded through one hole and back through a second hole to secure bonefragments and soft tissues such as cuff muscles to the collar, as willbe described in greater detail below in connection with FIGS. 6a to 6e .The suture holes 74 may be evenly spaced apart about the whole peripheryof collar 28 as illustrated, or they may be concentrated in portions ofthe collar which in use will be located near to particular bonefragments such as the greater and lesser tuberosities. The suture holes74 may be approximately 2.5 mm in diameter. As illustrated in FIG. 3,the sutures may extend from suture holes 74 in the collar to sutureholes 48 in the head part 42 of fixation plate 40. In an alternativeembodiment, in place of or in addition to the suture holes 74, thecollar 28 may have sutures 50 permanently coupled to or pre-attached tothe collar 28. The sutures may be attached for instance by crimping orby being tied to a suture hole 74. Some or all of the pre-attachedsutures may terminate at needles and/or anchors for coupling to bone orsoft tissue, or alternatively conventional surgical techniques may beused to attach the sutures to bone or soft tissue. The needles oranchors may be entirely conventional and so will not be furtherdescribed.

A surgical procedure for implanting the humeral head implant andarthroplasty plate of FIG. 2 to repair a fractured humeral head will nowbe described in connection with FIGS. 3 and 6 a to 6 e. It will beappreciated that details of the surgical procedure may vary, forinstance according to the preferences of the surgeon. As discussedabove, the arthroplasty plate and the humeral head implant of thepresent invention may be indicated for repair of three-part or four-partproximal humeral fractures. In a four-part proximal humeral fracture thehumeral head is a free fragment not coupled to any soft tissue anddeprived of a blood supply. The greater and lesser tuberosities aredetached. The greater tuberosity is displaced superiorly and posteriorlyby the attached rotator cuff, while the lesser tuberosity is retractedmedially by the attached subscapularis. The fractured end of the humeralshaft is displaced medially by the pull of the pectoralis major.Three-part fractures differ in that the greater or lesser tuberosityremains attached to the humeral head, which in consequence is rotatedinternally by the subscapularis tendon.

The surgeon must first gain access to the fractured humeral head. Thepatient is positioned so as to allow the surgeon free access to theinjured shoulder, for instance in a “beach chair” position, with theinjured arm hanging free, providing spaced for later manipulation of thearm. The fracture may be examined using fluoroscopy, including underinternal and external rotation. A deltopectoral exposure may be used toidentify the coracoid, acromium and deltoid insertion. The intervalbetween the pectoralis and the deltoid is developed and the incisionline is extended distally from the coracoids.

The exposure is through a 12-14 cm incision. The incision may be heldopen using self retaining retractors. Care must be taken to identify andretract the cephalic vein. The coracobrachialis is retracted mediallyand the pectoralis insertion at the floor of the deltopectoral intervalis located allowing the subacromial space to be developed to mobilisethe proximal deltoid.

The detached humeral head may then be removed (after releasing the headfrom the greater or lesser tuberosity in the case of a three-partfracture). The humeral head implant 20 may be provided in a range ofsizes to match the patient's natural humeral head. The appropriate sizeof articulation component 24 is selected, for instance by comparing thehumeral head to a gauge to measure its height and radius of curvature.Each articulation component 24 may have a corresponding collar 28, oreach articulation component may have a standard size recess 30 toreceive a single size of collar 28. The tuberosities must also bereleased from underlying soft tissues, taking care to protect theaxillary nerve when mobilising the lesser tuberosity and the attachedsubscapularis muscle tendon. The tuberosities are released so as toallow them to be coupled to each other and to the arthroplasty plate,passing around the prosthesis.

A surgical technique for implanting the arthroplasty plate is describedin greater detail in UK patent application 1101896.7 but is alsosummarised here. Initially a trial plate is applied to the surface ofthe humerus. The trial plate may be generally the same as the fixationplate 34, and in particular the bone contacting surface may be the sameshape. However, the trial plate does not include a barrel 52 and so itmay be freely positioned over the surface of the proximal, lateralhumerus. The anterior side of the trial plate is aligned with thebicipetal groove.

The trial plate further comprises a guide arranged to guide a 2 mm guidewire. The guide wire indicates where the prosthetic head (articulationcomponent 24) will be centred. This allows the surgeon to see that thetrial head will be in the correct position in relation to the calcarregion and the tuberosities. The guide wire is advanced slowly and thetrajectory may be verified under fluoroscopy. The guide wire serves totemporarily secure the trial plate to the bone. A trial head may becoupled to the guide wire. When correctly positioned the inferior aspectof the trial head should align with the medial end of the humeral head.

Once the position of the trial head has been confirmed, the surgeon maybe required to remove remaining fragments of the articulation surface ofthe humeral head. Typically, the articulation surface may already befractured or detached from the humerus. If required, a drill reamer maybe used to form a bore to receive the barrel 52. Alternatively, thebarrel 52 may extend above the fracture line of the humeral shaft 10, orminimal bone removal may be required.

The fixation plate 34 may then be secured to the lateral humeral surfacewith the connector assembly 38 extending towards the original positionof the humeral head. The trial head 208 may be temporarily coupled tothe taper 54 to check the final position of the neck axis.

The position of the trial head may then be adjusted using the adjustmentmechanism within the connector assembly 38 to determine the requiredposition for the humeral head implant 20. The position of the trial headmay either be determined before or after the shoulder joint is reduced,or further adjustment may be performed after the shoulder joint isreduced. The connector assembly is then locked in position and the trialhead removed.

Referring to FIG. 6a , after the arthroplasty plate has been secured tothe bone, the collar 28 is coupled to the bone fragments, and inparticular the greater and lesser tuberosities with sutures 50. FIG. 6ashows the collar 28 threaded with five sutures 50, and the tuberositiesare not shown. Initially the sutures are loosely coupled to the bonefragments to allow the collar 28 to be manoeuvred to be secured to thearticulation component 24, as shown in FIG. 6b . As the sutures may pullthrough tuberosity fragments in osteoporotic bone, preferably thesutures are additionally or only passed through the cuff tendons. Forthe humeral head implant 20 of the first embodiment of the invention,the articulation component 24 is screwed onto the collar 28 while thecollar 28 is held still, as will be described below in connection withFIGS. 6d and 6e . The humeral head implant 20 is then secured to thearthroplasty plate 22 as shown in FIG. 6c (illustrated without the bonefor clarity) by inserting taper 54 into the socket 60 and applying animpaction force to the humeral head implant 20. The sutures 50 couplingthe bone fragments to the collar 28 are then secured to the arthroplastyplate 22 and tightened to form a cage of sutures surrounding the bonefragments. The suture cage provides additional rigidity to the couplingbetween the arthroplasty plate 22 and the humeral head implant 20.

Referring to FIG. 6d , the arthroplasty plate 22 is shown secured to thehumerus shaft 10 and the sutures 50 are coupled to the collar 28. Forclarity the greater and lesser tuberosities 6, 8 are not coupled to thesutures 50. The fractured humeral head 2 is shown removed from thehumerus. The collar 28 is held still using a collar handle 80 which hastwin prongs (not visible) arranged to engage holes 72. The articulationcomponent 24 has a hexagonal slot 82 at the base of socket 60 arrangedto be engaged by a driver 84 to rotate the articulation component 24relative to the collar 28 to secure screw threads 68, 70 as shown inFIG. 6e . It will be understood that the sutures 50 must be kept looseuntil after the articulation component 24 has been screwed onto collar28 to allow space for the driver 84 to access the slot 82.

Compression, if required, between the articulation component 24 and thetuberosities may be provided by adjusting the distance between taper 54and the fixation plate 34 using the adjustment mechanism within theconnector assembly 38. Alternatively, the articulation component 24 maybe moved away from the fixation plate 34 to tension the sutures 50extending between the collar 28 and the head portion 42 of thearthroplasty plate 22.

Referring now to FIGS. 7 and 8, these illustrate a humeral head implant120 in accordance with a second embodiment of the present invention. Thesecond humeral head implant 120 is generally similar to the implant 20illustrated in FIGS. 4 and 5, and so corresponding features areidentified by the same reference numbers incremented by 100. As for thefirst embodiment, humeral head implant 120 comprises an articulationcomponent 124 and a collar 128. FIG. 7 shows the articulation component124 and collar 128 separated, and FIG. 8 shows a cross section whencoupled together. FIG. 3 additionally illustrates the second embodiment120 of the present invention when coupled to an arthroplasty plate 22.

The articulation component 124 comprises a convex bearing surface 160and a reverse surface 162 that includes recess 130. The convex bearingsurface 160 may be defined by a portion of a sphere. The reverse surface162 is substantially taken up by recess 130, which as illustratedextends across almost the full width of the reverse surface 162 withinrim 164. The recess 130 extends about socket 166 which is tapered andarranged to form a taper lock to taper 54 at the end of the neck part 26of arthroplasty plate 22.

Recess 130 forms an annular ring about socket 166. The outer edge ofsocket 166 is provided with an annular rib 180. Collar 128 comprises ahole 182 defined by a raised rim 184 corresponding to the outer shape ofsocket 166 and including an annular groove 186. Rim 184 is resilientlydeformable such that when forced over socket 166 it expands to allowgroove 186 to engage rib 180. Collar 128 snap fits to articulationcomponent 124 such that after the collar has been sutured to bonefragments and soft tissue the collar can be coupled to the articulationcomponent 124 before the articulation component 124 is coupled to taper54. When assembled, as shown in FIG. 8, the collar 128 is entirelyreceived within recess 130 such that it is flush with rim 164, orrecessed.

The articulation component 124 further comprises a hole 190 within therecess 130 and the collar 128 comprises a pin 192 arranged to bereceived within the hole 190. The pin and hole prevent the collar fromrotating relative to the articulation component when they are coupledtogether.

Around the periphery of collar 128 are suture holes 174. As for thefirst embodiment of the humeral head implant, sutures may bepre-attached to the collar. If sutures are supplied pre-attached to thecollar then the articulation component may be coupled to the collarbefore the implant is passed to the surgeon. However, an advantage ofproviding a separate collar is that the size of the implant is reducedwhen securing bone fragments and soft tissues in position, whichprovides the surgeon with more space to operate.

In addition to the screw fit and snap fit options for securing thecollar to the articulation component described above, it will be readilyapparent that the two components can be coupled together in other ways.For instance, the recess in the reverse surface of the articulationcomponent may taper and the collar may have a tapered edge and/ortapered neck hole to form a taper lock with the recess. Alternativelythey may be secured with screws or bolts, for instance passing throughthe collar into the reverse surface of the articulation component. Othercoupling options will be readily apparent to the appropriately skilledperson.

The implant of the present invention has been primarily described aboveas forming part of a humeral prosthesis. The implant is particularlysuitable for the repair of shoulder fracture indications because thereare typically three or four portions of fractured bone, and so thecollar assists in retaining the bone fragments. However, the implant mayalso form part of a modular prosthesis for implantation at the end ofanother long bone. For instance, the collar may form part of a femoralprosthesis for the repair of hip fractures. Commonly, the femurfractures across the neck. However, for some forms of femoral fracture,there are multiple portions of fractured bone and so the implant of thepresent invention may be useful for fixing the bone fragments inposition.

Other modifications to, and applications of, the present invention willbe readily apparent from the teaching herein without departing from thescope of the appended claims.

1. A surgical method comprising the steps of: removing at least part ofan articulating surface at an end of a bone; coupling a distal portionof an arthroplasty implant to the end of the bone, the arthroplastyimplant comprising a proximal neck portion extending from the distalportion; securing bone fragments to a collar with sutures extendingbetween the bone fragments or attached soft tissue and at least one of aplurality of attachment portions formed in the collar; couplingcomplementary features of the collar and a reverse surface of anarticulation component together to secure the collar to the reversesurface, the articulation component further comprising a bearingsurface; and coupling the articulation component to the proximal neckportion of the arthroplasty plate such that a neck hole of the collarpasses around the coupling between the proximal neck portion of thearthroplasty implant and the articulation component.
 2. The surgicalmethod of claim 1, wherein the step of coupling the distal portion of anarthroplasty implant to the end of the bone comprises securing afixation plate forming the distal part of the arthroplasty implant to alateral surface of the fractured end of the bone, the fixation platebeing coupled to a connector assembly defining the proximal neck portionand comprising a barrel with a bore and a connector rod, the connectorrod being arranged to slide within the bore of the barrel; sliding theconnector rod into or out of the barrel to adjust the length of theconnector rod extending from the barrel; and locking the position of theconnector rod within the barrel to rigidly space the articulationcomponent apart from the fixation plate.
 3. The surgical method of claim2, wherein the fixation plate further comprises a head portion proximalto the barrel, the head portion defining at least one suture hole,wherein the method further comprises the step of threading suturesbetween the attachment portions of the collar and the at least onesuture hole in the head portion of the fixation plate, the suturespassing through bone fragments or attached soft tissue to secure thebone fragments to the collar and the fixation plate.